Effect of long-range Coulomb interaction on shot-noise suppression in ballistic transport

We present a microscopic analysis of shot-noise suppression due to long-range Coulomb interaction in semiconductor devices under ballistic transport conditions. An ensemble Monte Carlo simulator selfconsistently coupled with a Poisson solver is used for the calculations. A wide range of injection-rate densities leading to different degrees of suppression is investigated. A sharp tendency of noise suppression at increasing injection densities is found to scale with a dimensionless Debye length related to the importance of spacecharge effects in the structure. @S0163-1829~97!09735-X# The phenomenon of shot noise, associated with the randomness in the flux of carriers crossing the active region of a device, has become a fundamental issue in the study of electron transport through mesoscopic devices. In particular, the possibility of shot-noise suppression has recently attracted a lot of attention, both theoretically and experimentally. 1 At low frequency ~small compared to the inverse transit time through the active region! the power spectral density of shot noise is given by SI5g2qI, where I is the dc current, q is the electron charge, and g is the suppression factor. When the carriers crossing the active region are uncorrelated, full shot noise with g51 ~Poisson statistics! is observed. However, correlations between carriers can reduce the shot-noise value, giving g,1. In real mesoscopic devices different types of mechanisms resulting in shot-noise suppression can be distinguished: ~i! statistical correlations due to the Pauli exclusion principle ~important for degenerate materials obeying Fermi statistics!, ~ii! short-range Coulomb interaction ~electron-electron scattering!, and ~iii! long-range Coulomb interaction ~by means of the self-consistent electric potential!. While the first two mechanisms have been extensively discussed in solid-state literature, 1 the last one has received less attention, 2 although its role in shot-noise suppression has been known for a long time in vacuum-tube devices. 3 The